In this investigation one hypothesis was considered. The question--does the use of a sub-culturally appropriate language have an effect upon achievement in an academic content--was tested. The subjects used in this investigation were children in a Follow Through Program in a school which is located in a disadvantaged neighborhood. None of the subjects had been in school for more than three years. The sample was a typical representation of the enrollment of schools in the city of Washington , D.C.-- 98 percent of the subjects were black. The instructional sequence was composed of concepts from nonmetric geometry. The language patterns used for the sub-culturally appropriate language were obtain ed from a two-year study in the speech-community of the given school. These language patterns were analyzed and classified by the Center for Applied Linguistics. After the instructional sequence was constructed, a parallel instructional sequence was rewritten in a subculturally appropriate language. Two groups of randomly assigned subjects were taught the appropriate sequence and given appropriate assessment tasks. The subjects taught and assessed using a subculturally appropriate language were able to successfully perform more task on the assessment task than those subjects who were taught and assessed using standard language. Hence, there exists some evidence to support the hypothesis that a sub-culturally appropriate language does have some effect upon achievement in academic content. The hypothesis was supported at the 0.05 level of significance. These findings suggest that further research is needed for the identification of contributing variables and the degree of interaction of each of these variables.